That 5% number seems extremely low to me. Is that maybe for all lithium batteries, like in phones and laptops? Or is that just car batteries?

The thing is, the vast majority of cars end up being stripped and recycled at the end of their life. Plenty of sources quote an 80+% recycling rate by weight. EV car batteries aren't going to just be thrown in the landfill, the materials are just too valuable. If they aren't being recycled now, I would expect they're being resold or stored until recycling capacity gets better.